Highly sensitive and specific monoclonal antibodies which we have produced to human varicella-zoster virus (VZV) and the Delta herpesvirus (DHV) strain of simian varicella virus, together with immunoprecipitation, protein transfer technics, and immunoassays employing antibodies labeled with fluorescein, radioisotopes, enzymes or other labels will be used to acquire a better understanding of varicella infections and mechanisms of humoral immunity. 1. Monoclonal antibodies will be used to develop sensitive immunoassays for use in studying the initation, spread, persistence and humoral immune responses to VZV and DHV infections in the patas monkey model. 2. The monoclonal antibodies will be used for precise antigenic analyses of the human and simian varicella viruses and to: a. Identify antigens involved in neutralization, attachment to host cells and other immunological reactions. Identify viral antigens expressed on the host cell surface and study their roles in humoral immunity. b. Explore the mechanisms of complement-dependent neutralization and antibody enhancement of infectivity, and study the role of non-neutralizing anti-bodies in enhancing or attenuating infection. c. Determine the extent of antigenic variation in VZV and DHV strains. 3. Monoclonal antibodies will be used as immunoadsorbents to purify viral proteins for use as immunizing antigens or serological reagents of improved specificity. The studies will provide basic information on varicella infection and immunity, and will provide methods for more rapid and accurate diagnosis of infection. These are needed for control of infection in high-risk populations and for guidance in the administration of antiviral agents.